The present invention relates to an improvement in wound capacitors, and, more particularly, to the connection of electrical terminals to the ends of wound capacitor sections.
Conventional wound AC capacitors are constructed by continuously winding two electrode materials with an insulating layer separating the two throughout their total length. The dimensions of the electrodes as well as the dielectric separating these two structures determine the capacitance of the wound structure. Generally, the electrodes are arranged to continually extend from alternate ends of the wound capacitor section thus providing a convenient means for terminating the two electrodes. All of the adjacent convolutions of one electrode are short-circuited at one end of the capacitor section, while all of the adjacent convolutions of the other electrode are short-circuited at the opposite end of the winding. Short-circuiting of adjacent convolutions at either end of the winding may be accomplished through any of a number of known methods such as soldering, welding, or spray metal coatings.
Soldering of electrical terminals to a capacitor section has the disadvantage of requiring a flux for an efficient solder connection. The presence of the flux, some of which remains after the soldering is completed, contaminates the capacitor section. Depending upon the particular construction of the electrodes of a wound capacitor, welding of electrical terminals to the capacitor likewise presents disadvantages. The localized weld connection of a terminal to a capacitor section may cause oxidation at these areas resulting in high resistance connections. U.S. Pat. No. 3,067,488 illustrates one example of a welded electrode structure. The terminal connections are welded to the exposed foil electrodes, which may be aluminum or any other metal. The welds occur at points 11 provided by projections 9 on the surface of the terminal material, while the balance of the terminal has a coating of insulating material thereon to prevent welding. It is at these points 11 that oxidation may occur and cause a high resistance connection.
A sprayed metal coating onto the ends of the capacitor section, such as shown in U.S. Pat. No. 2,915,808, may be used to terminate both ends of the wound capacitor and provide for connection of electrical terminals. Electrical terminals may thereafter be attached to the sprayed metal coating as by soldering, as shown in U.S. Pat. No. 2,940,161. Even this combination of sprayed metal coating plus soldering of electrical terminals encounters the disadvantage noted above with respect to soldering fluxes.